Compounds that are capable of generating free radicals by thermal, photochemical, or redox decomposition are used as initiators in polymerization of vinyl monomers. Many commercially available initiators, including various kinds of peroxides, persulfates, and azos are used to produce a large quantity of polymers and copolymers. In most cases these initiators yield random copolymers when used to initiate copolymerization of two (or more) different monomers. As described in the Textbook of Polymer Science by Billmeyer (John Wiley & Sons, 1984, pages 120-121): "Methods of synthesis of polymers containing long sequences (particular monomeric repeating units) are of interest, since they may lead to polymers with properties widely different from those of either homopolymers or random copolymers."
Polymers with long sequences of two monomers can be categorized as block copolymers or graft copolymers. In block copolymers the sequences follow one another along the main polymer chain, EQU --AABB--BBAA--AABB--, etc.
Block copolymers have unique and highly desirable properties as compared to random copolymers or the blend of two homopolymers. Therefore, there is a great interest in preparing them. Few techniques described in the literature satisfy the need.
In this invention, a new type of initiator, characteristic of polymers capable of initiating polymerization via a radical type mechanism is disclosed. This polymeric initiator can be used to prepare block and other types of polymers which cannot be readily prepared using conventional initiators. The polymeric initiator containing more than one initiating group can be partially decomposed to initiate one monomer to give a still reactive prepolymer which can further initiate polymerization of another monomer by decomposing the remaining initiating group to afford a block copolymer. Similarly, a multiblock copolymer can be prepared if the polymeric initiator is homolytically cleaved in the presence of several monomers added sequentially.
Furthermore, with ever increasing usages of water soluble polymers and co-polymers in industries such as wastewater treatment, cooling, boiler and deposit control, coating, textile, mining, detergency, cosmetics, and paper, etc., there is an urgent need to synthesize novel water soluble block copolymers for this broad range of applications.
It is thus an object of this invention to synthesize a novel polymeric initiator that is capable of initiating polymerization of vinyl monomers into water soluble polymers or copolymers.
It is a further object of this invention to prepare distinctive water soluble polymers or copolymers for water treatment applications.